NSW Scientific Committee - final determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the "Loss and/or degradation of sites used for hill-topping by butterflies" as a KEY THREATENING PROCESS on Schedule 3 of the Act. Listing of Key Threatening Processes is provided for by Part 2 of the Act.

The Committee previously made a Preliminary Determination regarding the "Loss of butterfly hill-topping sites". The Committee has decided that the "Loss and/or degradation of sites used for hill-topping by butterflies" is a more appropriate name for this Process.

The Scientific Committee has found that:

1. Hill-topping in butterflies is a very complex behaviour that often facilitates meeting of the sexes (Shields, 1967; Atkins, 1975; Common and Waterhouse, 1981; Baughman and Murphy, 1988; Sands, 1993; New, 1997; Newland, 1997). Hill-tops act as a focus for mating. Many butterfly species, especially in the families Hesperiidae, Papilionidae and Lycaenidae appear to be obligatory hill-toppers and tend to congregate on hill or ridge tops that are usually higher than the surrounding countryside. The nature of the sites varies and a site may be as small as a few square metres or may cover several hectares, or display minor or very marked topographic relief. The same sites are used year after year, whilst apparently similar nearby sites may not be used. Sites do not necessarily provide nectar food sources for the butterflies nor food plants for the next generation of caterpillars. Hill-top aggregations are essential for continuity of the reproductive cycle of some butterfly species, and hill-top sites may constitute vital focal points for such aggregations. The importance of hill-topping sites is out of proportion to their extent, so that a small area can be vital to the survival of species over a larger area (Smithers 1996). Hill-topping is often found in species which seasonally or habitually have low density populations and which have a greater need to facilitate male - female encounters, such as in the drier areas of NSW (G. Newland pers. comm). Well known examples of butterfly hill-topping sites are Mt Warning, Razorback Lookout, Lions Lookout, Peates Mountain Mt Ramornie (all in northern NSW), Mt Sugarloaf, near Newcastle and Cook Trig in Wahroonga. The importance of butterfly hill-topping sites has been recognised in the nomination and listing of Mt Ramornie (Nymboida Invertebrate Habitat), on the Register of the National Estate.

2. Hill-topping butterflies are almost entirely males that frequently take flights over the area. These flights follow a more or less set pattern, with 'patrolling' males investigating females that enter the area. Most of the females that fly to the hilltop are virgin. These females soon mate, and after mating leave the site to seek appropriate food plants, which may be several kilometres distant on which to lay their eggs.

3. Hill-top physiognomy is important to hill-topping butterfly species (Smithers, 1996; New 1997). Small changes in the appearance of a site can result in males not recognising it as a suitable site. Factors which determine whether a site is used or not can be quite subtle (Baughman and Murphy, 1998) so that changes causing butterflies to abandon the site can be quite small (Smithers 1996). Disturbance of plants on, or topography of, the hill-top, or to its slopes and immediate surroundings, may render it unsuitable to butterflies as a hill-topping site. In the absence of other hill-topping sites, butterflies may disappear entirely from a district. Loss of hill-top habitats throughout NSW would affect butterfly species which rely on such sites and some local extinctions have undoubtedly occurred due to hill-top alteration.

4. "Loss and/or degradation of sites used for hill-topping by butterflies" is one of a number of threats to butterflies in NSW. Loss of hill-topping sites due to habitat alteration (e.g. loss of vegetation for agriculture, urban development, forestry, tourist development, communication towers or power transmission lines), may lead to loss of perching or patrolling sites for male butterflies, loss of focal points for mating and thus local extinctions. For example, at Mt Sugarloaf, near Newcastle, since the installation of communication towers there has been a decline in numbers of hill-topping butterfly species and there is evidence of decline or local extinction of Acrodipsas brisbanensis, Delias harpalyce, Delias nysa and Dendorix epyarbas (A. Atkins pers. comm.). In Queensland, disturbance of a hill-topping site in Brisbane Forest Park appears to have led to the local extinction of several species (which also occur in NSW), Hesperilla crypsigramma, Hypochrysops ignitus and A. brisbanensis (D. Sands pers. comm.). The determination to list the butterfly community at Mt. Piper in Victoria as a Threatened Community under the Fauna and Flora Guarantee Act, 1988 (Jelinek et al., 1994), further recognises the importance of hill-topping.

5. Butterflies which hill-top in NSW and whose populations could become threatened if hilltopping sites were lost include: Hesperiidae such as Neohesperilla xanthomera and Hesperilla crypsigramma; Lycaenidae such as Acrodipsas arcana, Acrodipsas brisbanensis, Acrodipsas cuprea, Acrodipsas mortoni, Acrodipsas myrmecophila, Ogyris genoveva, Ogyris olane, Ogyris oretes, Deudorix epijarbas and Candalides cyprotus; and Theclinae such as Hypochrysops ignitus and Hypochrysops delica.

6. In view of 1, 2, 3, 4, and 5 above, the Scientific Committee is of the opinion that the "Loss and/or degradation of sites used for hill-topping by butterflies" could cause butterfly species, populations and communities that are not threatened to become threatened.